Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$64.48	11.820%	$72.1015	$72.10	$72.10	$72.10
Purchase #2	$158.28	13.757%	$180.0546	$180.05	$180.05	$180.10
Purchase #3	$146.73	5.389%	$154.6373	$154.64	$154.65	$154.60
Purchase #4	$144.65	9.277%	$158.0692	$158.07	$158.05	$158.10
Purchase #5	$209.86	4.560%	$219.4296	$219.43	$219.45	$219.40
Purchase #6	$55.41	7.314%	$59.4627	$59.46	$59.45	$59.50
Purchase #7	$246.68	6.403%	$262.4749	$262.47	$262.45	$262.50
7 purchase totals =	$1,026.09		$1,106.2298	$1,106.22	$1,106.20	$1,106.30